The proposed research will examine whether the striking changes in catecholamine function observed during development in brain areas involved in vocal learning and/or the motor control of vocalization contribute to vocal learning and/or the differentiation and development of these brain areas. Since noradrenergic function peaks in many of these brain areas during the period when juveniles first memorize vocal models, the first study will examine whether lowering brain norepinephrine levels at this time disrupts the process of vocal learning in both males and females. It will also determine whether this manipulation during development grossly alters adult social behavior, neuroanatomy and/or brain monoamine levels. Study 2 will examine whether early social deprivation retards the development of brain catecholamine function and whether brain catecholamine function is affected by juveniles' first interaction with a potential vocal model, suggesting an involvement in memorization of the vocal model. Study 3 will examine whether the use of norepinephrine receptor antagonists during the period of vocal learning disrupts the ability to learn from a tutor, the type of receptor(s) involved, and if disruption occurs, whether it persists beyond the period of drug administration. It will also determine if such treatment causes gross changes in brain anatomy or adult monoamine function. The fourth experiment will examine whether treatment with a dopamine receptor antagonist during the period of motor practice disrupts either the memorization or production of learned vocalizations either temporarily or long term. It will also determine whether this treatment has long-lasting effects on adult monoamine function. The issues addressed by this research are relevant to problems of human brain function and behavior. This research will assess possible contributions of catecholamines to the development of a complex social behavior. It will also look for evidence suggesting that catecholamines are involved in stimulating some of the dramatic neuroanatomical changes which occur in brain areas controlling vocalization during the development of this behavior. Disruptions of catecholamine function have been implicated in a number of mental disorders in humans. Data providing a clearer picture of the normal involvement of brain catecholamines in the development of vocal communication and social behavior as well as the effects of experimentally-induced disruptions of catecholamine function on behavior should be useful to those attempting to understand how neurotransmitter function affects behavioral and neural development.